any structural anomaly in the sensory cells of the organ of Corti which are in synaptic contact with sensory as well as efferent fibers of the auditory nerve; there is a single row of flask-shaped inner hair cells tightly surrounded by supporting interphalangeal cells; the apical end of each cell is anchored to the cuticular plate and about 100 stereocilia arranged in a more or less linear (or shallow) U-shaped pattern extend from the cell's surface through the cuticular plate into the endolymphic space inferior to the tectorial membrane